output_compression.rb

#
# OutputCompression plugin
# made by http://craz8.com/svn/trunk/plugins/output_compression/
#

module OutputCompression

  protected
    def compress_output
      return if response.headers['Content-Encoding'] || request.env['HTTP_ACCEPT_ENCODING'].nil?
      begin
        request.env['HTTP_ACCEPT_ENCODING'].split(/\s*,\s*/).each do |encoding|
          # TODO: use "q" values to determine user agent encoding preferences
          case encoding
            when /\Agzip\b/
              StringIO.open('', 'w') do |strio|
                begin
                  gz = Zlib::GzipWriter.new(strio)
                  gz.write(response.body)
                  response.body = strio.string
                ensure
                  gz.close if gz
                end
              end
            when /\Adeflate\b/
              response.body = Zlib::Deflate.deflate(response.body, Zlib::BEST_COMPRESSION)
            when /\Aidentity\b/
              # do nothing for identity
            else
              next # the encoding is not supported, try the next one
            end
          logger.info "++ Response body was encoded with #{encoding}" 
          response.headers['Content-Encoding'] = encoding
          break    # the encoding is supported, stop
        end
      end
      response.headers['Content-Length'] = response.body.length
      if response.headers['Vary'] != '*'
        response.headers['Vary'] = response.headers['Vary'].to_s.split(',').push('Accept-Encoding').uniq.join(',')
      end
    end

    def self.included(base)
      base.send :instance_method, :compress_output
    end

end